United States
Department of
Agriculture
Site Treatments
Influence
Development of a
Young MixedSpecies Western
Larch Stand
Forest Service
Intermountain
Research Station
Research Paper
INT-364
June 1986
Dennis M. Cole
Wyman C. Schmidt
LP
WL
OF
SAF
ES
This file was created by scanning the printed publication.
Errors identified by the software have been corrected;
however, some errors may remain.
THE AUTHORS
DENNIS M. COLE is a research silviculturist with the
Silviculture of Conifers in Montane and Subalpine
Forest Ecosystems of the Intermountain and Northern
Rocky Mountain West research work unit at the Forestry
Sciences Laboratory, Bozeman, MT. His studies have
focused on lodgepole pine silviculture, particularly
growth and yield relationships, culture of immature
stands, and management of the species in the face of
major insect and disease problems.
WYMAN C. SCHMIDT is a research silviculturist and
Project Leader of the Silviculture of Conifers in
Montane and Subalpine Ecosystems of the lntermoun·
tain and Northern Rocky Mountain West research work
unit at the Forestry Sciences Laboratory, Bozeman,
MT. Dr. Schmidt's research has focused on the ecology, regeneration processes, stand development, and
related cultural practices in coniferous forests of the
Intermountain West. Much of his research has centered on the interrelationships of timber, water, and
other resources as well as the interaction of cultural
practices with insect pests such as western spruce
bud worm.
ACKNOWLEDGMENTS
We gratefully acknowledge previous researchers
involved in the initial planning, installation, and subsequent remeasurements of this study, including
Kenneth N. Boe, Steven A. Haglund, Ward W.
McCaughey, Arthur L. Roe, Jack A. Schmidt, Raymond
C. Shearer, and Anthony E. Squillace.
July 1986
Intermountain Research Station
324 25th Street
Ogden, UT 84401
Site Treatments Influence
Development of a young MixedSpecies Western Larch Stand
Dennis M. Cole
Wyman C. Schmidt
INTRODUCTION
More intensive management could be applied to many
young stands in conifer forests of the Northern Rockies.
Vast areas are stocked with stands that contain a mixture of conifer species. An important mixed species
cover type in this region is the western larch type
(formerly called the larch-Douglas-fir type)(Society of
American Foresters 1980). It is usually dominated by
western larch (Larix occidentalis Nutt.) and Douglas-fir
(Pseudotsuga menziesii var. glauca [Beissn.] Franco); but
also has appreciable amounts of Engelmann spruce
(Picea engelmanii Parry) and subalpine fir (Abies
lasiocarpa [Hook.] Nutt.). Species sometimes occurring in
the cover type are lodgepole pine (Pinus contorta var.
latifolia Engelm.), western white pine (Pinus monticola
Dougl.), western hemlock (Tsuga heterophylla [Raf.]
Sarg.), and western redcedar (Thuja plicata Donn ex D.
Don). The exact species composition in the western larch
type is determined largely by the successional stage of
the stand and the physical environment in which the
stand occurs. Usually the above-mentioned mixture of
conifer species occurs in habitat types of the Pseudotsuga
menziesii and Abies lasiocarpa successional series
(Daubenmire and Daubenmire 1968; Pfister and others
1977).
Mature and overmature forests of the western larch
type, containing appreciable amounts of larch, Douglasfir, spruce, and white pine in the overstory, have long
been sought for timber harvest. Many of the accessible
mature stands have been harvested and regenerated to
young mixed-species stands that show the influence of
the particular cutting system and site preparation
methods that were used. Knowledge of the effects on
future stands of cutting systems and various site preparation and vegetation-manipulation treatments is an
important consideration for proper management of
stands still to be harvested.
Because of its rapid growth, excellent wood, desirable
esthetic qualities, and low incidence of insect attacks,
disease, and defects, western larch is usually featured in
management of the western larch type. But because
most managers seek to maintain a mixture of species,
Douglas-fir, Engelmann spruce, and lodgepole pine are
also encouraged in the regeneration process. These objectives usually result in even-age management of stands of
the western larch type, including either clearcutting,
shelterwood, or seed-tree methods of regeneration
(Schmidt and others 1976). Each of these cutting
methods can provide favorable conditions for natural
regeneration of the favored species- but depending on
seedbed and understory vegetation conditions following
cutting, the composition, density, and growth of the
future stand can vary widely (Polk and Boe 1951; Roe
1955; Schmidt 1969).
Polk and Boe (1951) and Roe (1955) concluded that
desired composition of the future stand can neither be
attained nor maintained through cutting method alone;
seedbed preparation and later stand improvement practices are necessary. Specifically, practices are required
that obtain establishment of desired tree species before
shrubs and other vegetation overwhelm the site. Roe
(1955) studied the relative need for sunlight and mineralsoil seedbeds of larch and its common associates in the
western larch type at Terrace Hill on the Coram
Experimental Forest in northwestern Montana. He
described the relationships among method of cutting,
proportion of ground surface in favorable seedbed, and
resultant stocking percentages of each species.
Schmidt (1969) later reported on seedling and early
sapling development and concluded that site
preparation-in the form of mechanical scarification,
prescribed burning, and slashing of competing shrubsinfluenced not only regeneration establishment, but subsequent seedling development. He found, after 12 to
15 years, that larch regenerated abundantly, grew
rapidly, and became dominant where prescribed burning
or mechanical scarification provided a sufficient area of
ash or mineral soil seedbeds and reduced the amount of
competing vegetation. Spruce seedlings also required
mineral soil for successful establishment but grew slowly
on the exposed seedbeds favored by larch. In contrast,
Douglas-fir was insensitive to seedbed condition in the
regeneration phase, but tended to dominate the stands
where seedbeds had little or no preparation and larch
competition was light.
From the above observations, Schmidt (1969) predicted
that the direct effects of seedbed and understory would
continue to diminish and the effects from differences in
stand density and shade tolerance would increase as the
stand grew past the early" sapling stage. This report
tests this hypothesis by comparing subsequent growth
patterns against site treatments in the 25-year-old stand.
STUDY DESCRIPTION AND
PROCEDURES
RESULTS
A brief review of the 15-year results shows that the
seed trees, adjacent timber, and small understory trees
left after logging produced enough seed to adequately
stock, and in most cases overstock, the study area. The
mineral soil seedbeds were especially overstocked,
primarily with larch and spruce (Schmidt 1969). Nonscarified forest floor seedbeds had only about one-third
the stocking of the mineral soil seedbeds and had higher
proportions of Douglas-fir and subalpine fit in comparison to larch and spruce. These treatment-related differences in stocking density and composition provided the
basis for earlier forecasts of significant differences
among the species in future survival, growth, vigor, and
relative expression of dominance in the stand (Schmidt
1969).
The earlier report (Schmidt 1969) of growth differences
among species featured dominant trees, but after 25 years
many dominant sample trees were dead. Therefore,
growth results presented here are in terms of all trees
surviving on the quadrats at the last measurement.
Height growth from 15 to 25 years of age and breast
height diameter at 25 years of age were analyzed for the
major species regenerated in the study area: western
larch, lodgepole pine, Douglas-fir, Engelmann spruce,
and subalpine fir. With the additional 10 years of stand
development, growth effects have become more evident,
earlier conclusions can be tested, and still stronger inferences for future stand development can be made.
This study was established at Terrace Hill on Coram
Experimental Forest in northwestern Montana within a
large, recently logged stand of western larch and
Douglas-fir. The stand was located on a lower northeast
slope and had a larch site index of 58 ft at 50 years-a
medium site. The original stand consisted primarily of
western larch (WL) and Douglas-fir (DF), but contained
small numbers of spruce (ES), western white pine
(WWP), lodgepole pine (LP), subalpine fir (SAF), and
western hemlock (WH). The stand was logged in 1943,
leaving about five healthy, well-distributed dominant
larch seed trees per acre and a heavy residual understory
of trees (chiefly subalpine fir and tall shrubs such as yew
[Taxus brevifolia Nutt.]). Slash was piled and burned in
1944. In 1945, the residual understory of trees and tall
shrubs was slashed on an area of 8 acres and an equalsize area left unslashed. The ground surface after logging and burning included undisturbed forest floor and
mineral soil exposed by tractor skidding, road construction, and slash burning. These operations left four generalized combinations of seedbed-vegetative competition
conditions for study: (1) unslashed-unscarified, (2) unslashedscarified (scarified only), (3) slashed-unscarified (slashed
only), and (4) slashed-scarified. It is important to understand that unslashed and unscarified treatments still
received some soil disturbance in the course of the logging process.
Fifteen milacre (0.0004-ha) plots were randomly established for each of the four seedbed/competing vegetation
conditions, making a total of 60 sample plots. In 1949,
after several years had been allowed for adequate seedfall, reproduction was tallied by species. Following the
reproduction tallies, the study was converted to a stand
development study and the initial seedling establishment
and early seedling development results were reported
(Roe 1955). Upon conversion to a stand development
study, all tree seedlings on the milacre study plots were
recorded by species and measured for height to the
nearest 0.1 ft (3 em) and their vigor subjectively classified as good, fair, or poor, on the basis of crown length
and density, needle color and length, and prior growth.
As the trees grew into and beyond the sapling stage at
the third and fourth measurements, crown class of trees
on the milacre plots was also recorded. At the fourth
measurement at 25 years, diameter at breast height
(d.b.h.) was also measured on all trees exceeding 4.5 ft
(1.37 m) in height.
Data from this completely randomized study were subjected to analysis of covariance to determine the statistical significance of treatments on growth of the different
species. Trees-per-acre stocking at establishment in 1949
was used as the covariate in these analyses. Trends in
stocking, composition, vigor, and dominance were also
analyzed.
Diameter Growth
Several treatments had produced no Engelmann
spruce or subalpine fir of breast height at the time of
the last measurement; therefore only western larch and
Douglas-fir were analyzed for diameter growth differences among species and treatments. Treatment effects
differed significantly (p=0.05) between western larch and
Douglas-fir. Scarification resulted in greater diameters
among western larch than Douglas-fir (fig. 1). Slashing
promoted growth of larch more than Douglas-fir, but
only on unscarified plots (fig. 1). The largest diameters
were registered for larch on unscarified, slashed plots;
the smallest diameters were also larch, but where no
slashing or scarification had occurred. The slow diameter
growth of larch in unscarified areas likely results from
the intolerance of larch to competition from overtopping
residual vegetation in the unslashed plots. The rapid
diameter growth of larch is likely a consequence of limiting competition by slashing but not scarifying seedbeds.
In contrast to larch, slashing on unscarified plots
reduced diameter growth of Douglas-fir. This effect
seems to be related to the strong growth performance of
the larch; the higher densities and faster growth of larch
apparently suppress diameter growth of Douglas-fir
established at the same time. Slashing had virtually no
effect on either larch or Douglas-fir on scarified plots.
2
3.0
WESTERN LARCH
f<'~Q
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en
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DOUGLAS-FIR
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Ill
c
1.0
•
•
0 ---·------------·•
•
UNSLASHED
SLASHED
UNSLASHED
•
•
SLASHED
Figure 1.-Effect of scarification and slashing on diameter
growth to 25 years of age.
Height Growth
]
]
Height growth differences among western larch,
Douglas-fir, Engelmann spruce, and subalpine fir were
not significant when adjusted for stand density, but
treatments did significantly affect (p=0.05) height
growth of all species (fig. 2). Slashing of understory
shrubs and trees left after the seed tree harvest resulted
in significantly greater height growth of regeneration
than when left unslashed, while scarification significantly reduced height. growth only in plots where slashing had occurred. The best height growth occurred where
no scarification occurred but where residual trees and
shrubs were slashed. In contrast, the poorest height
growth occurred where scarification had occurred, but
where no slashing was done.
Seedling vigor-classified on the basis of early growth,
foliage density, and needle color and length-was a good
indicator of subsequent height growth in earlier measurements of this study (Schmidt 1969). For example, from
age 10 to 15, good-vigor larch, lodgepole pine, Douglasfir, and subalpine fir grew about two and six times
faster than their fair-vigor and poor-vigor counterparts.
Good-vigor spruce grew only about twice as fast as their
poor-vigor counterparts. Each vigor class of western
larch and lodgepole pine grew about twice as fast as
other species of corresponding vigor classes during that
period.
Tree vigor at the last measurement was again considered as a means of evaluating height growth. A discriminant analysis was made to determine whether vigor
could be classified using species and treatment variables;
however, no effective discriminator involving treatments
was found. Therefore, vigor was evaluated as before as
an influence on growth, irrespective of treatments.
5
4
1-
u.
u;
a:
>
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........................
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0
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UNSLASHED
........................ ..
................................
2
...."::z::
"w
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1
0~--·-------------------------------·--
•
UNSCARIFIED
Figure 2.-Effect of scarification and slash·
ing on height growth of major species from
age 15 to 25 years.
3
•
SCARIFIED
height growth than the good-vigor trees of all other species, but the good-vigor Douglas-fir were accelerating.
The shade-tolerant subalpine fir and spruce lagged
behind in keeping with their normal understory positions
in this forest type. How differential species performance
influenced the character of the stand at age 25 is discussed in the following section.
The same general height growth relationships apparent
in the 10- to 15-year age period among and between species and vigor classes were also apparent in the 15- to
25-year age period (fig. 3). On the basis of average periodic annual increment (P AI), however, growth rate
differences of the good-vigor class lessened for most species, as did differences between species within the same
vigor class. Douglas-fir was the exception; trees in the
good-vigor class at 15 years of age increased in height
PAl from 15 to 25 years of age, suggesting that favorably located Douglas-fir seedlings of good vigor can be
expected to gradually increase their growth rate and
maintain their vigor in the first 25 years of stand
development. The two seral species, larch and lodgepole
pine, continued to exceed other species in rate of height
growth, but trees originally noted for good vigor grew
substantially slower from age 15 to 25 than they had
from age 10 to 15. Differences in PAl between the two
growth periods were less apparent and less consistent
for the fair and poor vigor trees. Major seral species, in
particular, were influenced in the regeneration stage by
seedbed conditions and competing vegetation; with time
this becomes less important than intertree competition.
A composite of the total 25-year period shows the two
sera! species-lodgepole pine and western larch-making
the greatest total height growth (fig. 4). Even the fairvigor lodgepole pine and western larch had greater
30
25
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15
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Figure 4.-Total height at age 25 of five
different conifers in three different vigor
classes.
..:z
w
w
a:
::E
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Stand Character
0
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...::r:
Western larch and spruce comprised two-thirds or
more of the large number of trees per acre established
on seedbeds that had been scarified; Douglas-fir and
subalpine fir comprised about two-thirds of the lessdense regeneration in tlie treatments where the forest
floor was unscarified (Schmidt 1969). But total stand
density, species stocking frequency, and stocking frequency of dominant trees have changed markedly during
the 25 years of study (table 1). Where the forest floor
was not scarified, initially modest stand densities
increased by about 1,000 trees per acre. Where scarified,
stand densities increased substantially where understory
had not been slashed-apparently due to continued
regeneration of the more tolerant species from the
residual seed source. Where scarified and slashed, stand
density peaked at age 15 but by age 25 declined below
the density at age 10, due mainly to mortality of western larch from interspecies competition. At age 15, larch
CJ
iij
::r:
~
0.5
VIGOR
0
a:w
GOOD
0.
0
Figure 3.-Periodic annual height increment
for the age periods 10 to 15 and 15 to 25 of
five conifers in three different vigor classes.
4
Table 1.-Stand density and stocking frequency of all trees and dominants by
age and treatment
Density
of
regeneration
Stocking frequency
WL 1
Other2
Treatment
Age
Unslashed,
unscarified
10
15
25
3,140
4,210
4,267
3 33(33)
40(40)
40(40)
67(53)
73(40)
73(36)
7(0)
13(0)
7(0)
20(7)
20(7)
33(7)
(7)
(13)
(17)
Unslashed,
scarified
10
15
25
13,390
17,330
16,733
100(93)
100(93)
87(67)
80(0)
80(0)
73(13)
80(0)
100(0)
93(0)
60(0)
87(0)
80(0)
(7)
(7)
(20)
Slashed,
unscarified
10
15
25
3,270
4,410
4,067
67(47)
73(47)
53(33)
73(53)
67(46)
67(40)
20(0)
40(0)
47(0)
33(0)
33(0)
33(0)
(0)
(7)
(7)
Slashed,
scarified
10
15
25
10,470
12,800
9,467
93(73)
87(66)
87(59)
80(13)
80(7)
67(7)
73(0)
80(0)
80(0)
7(0)
20(0)
20(0)
(14)
(27)
(34)
Trees/acre
DF
ES
SAF
---------------Percent---------------
1
Relative shade tolerance ranking of species is from left to right, least (WL) to most
(SAF).
2 0thar species were primarily lodgepole pine and a few western white pine.
3
Frequencies in parentheses are the percentages of milacre quadrats in which dominant trees of the species occur.
had occurred. These effects are consistent with the relative shade tolerance ranking of subalpine fir.
At 25 years of age, more than three-fourths of the
good-vigor larch occurred on the treatments receiving
scarification. Conversely, the percentage of poor-vigor
larch there increased from 5 to over 25 percent. More
than three-fourths of poor-vigor larch occurred on scarified plots-an apparent consequence of the high stand
densities on scarified treatments.
The reduction in numbers of good-vigor spruce at age
25 occurred almost exclusively on scarified treatments,
even though such sites supported nearly all of the
remaining good-vigor spruce. Like larch, these reductions
in vigor indicate that the heavy stand densities in the
scarified treatment areas reduce spruce vigor, despite
the encouragement of spruce establishment by scarification.
Initially, good-vigor Douglas-fir occurred at about the
same frequency on all treatments, but by age 25, twothirds of the good-vigor Douglas-fir were found on
unscarified treatments. Poor-vigor Douglas-fir increased
from 10 percent to more than 35 percent of trees at age
25. The highest proportion of good-vigor trees and the
lowest proportion of poor-vigor trees occurred on the
slashed-only treatment.
occurred uniformly on scarified areas and dominated up
to 90 percent of such areas, but by age 25 their stocking
distribution had declined and they dominated only about
two-thirds of scarified area. Most of the decline in larch
dominance on scarified seedbeds occurred where competitive shrubs and understory trees were not removed.
Larch only stocked 40 to 50 percent of the unscarified
areas, but where they were able to establish, they
usually became dominant.
Like larch, spruce was well-distributed, stocking at
least 50 percent of the area where slashing had occurred
and over 80 percent of the area where scarification had
occurred. Because of its slow juvenile growth, spruce
was overtopped by other species and exhibited no dominance in any treatment.
Douglas-fir was well-distributed at age 25, indicating
little establishment preference for any treatment. In
unscarified treatments, Douglas-fir was able to express
dominance about equally with larch, apparently because
of significantly lower larch stocking densities there; but
it expressed little dominance in scarified areas where
larch and lodgepole pine dominated.
Tree Vigor
Considering the treatment-related differences in stocking and dominance, changes in the relative vigor status
of the species were expected. Initially larch, Douglas-fir,
spruce, and subalpine fir each had about 60 percent of
seedlings classified as good vigor, but by age 25 each
except subalpine fir had declined to about 30 percent
high-vigor trees. Overstocking was taking its toll on
vigor.
The vigor of subalpine fir increased slightly to about
65 percent classified as good vigor. This slight increase
occurred on the scarified-only treatment, but was offset
by a similar decrease on the treatments where slashing
DISCUSSION AND CONCLUSIONS
The Terrace Hill study demonstrates that seed-tree
cutting in the western larch type allows considerable
flexibility in guiding the composition and development of
the new stand, depending on seedbed and understory
vegetation treatment in the establishment phase. It also
demonstrates the consequences of failing to control density through the late sapling-early pole stage-in terms
of height and diameter growth, dominance, and vigor.
5
Several conclusions are drawn from the study:
1. Seed-tree cutting in the western larch type generally leaves interspersed areas of scarified soil and
undisturbed forest floor, on which regeneration of mixed
species generally ranges from adequate to overstocked.
2. For all species in general, slashing of residual
understory trees and shrubs results in greater height
growth. The greatest height growth occurs in the
slashed-unscarified areas where both effects of stand
density and understory vegetation are minimized.
3. Larch is dominant or codominant in early stand
development, particularly on scarified areas. Douglas-fir
is codominant with larch in early stand development
where no scarification occurs.
4. After 25 years, good-vigor larch and lodgepole pine
were able to maintain significantly faster height growth
on all treatments than the other major species; all vigor
classes of larch grew significantly faster in diameter
than Douglas-fir, except on the unslashed-unscarified
treatment.
5. Although considerable flexibility is possible in the
seed-tree system in guiding initial species composition,
density of regeneration, and early growth through
scarification and understory vegetation control, the best
opportunity for long-lasting influence on composition
and growth of the stand is through early cleaning and
thinning operations.
6. The first 25 years is a dynamic period in, the life of
a stand in this forest type, and it is then that managers
have the greatest opportunity to shape the character of
the future forest in terms of density, composition, structure, and timber yield.
As pointed out earlier (Schmidt 1969), precise regulation of stocking is difficult in natural regeneration systems because of yearly variations in seed production,
germination, and seedling survival among species; therefore, cleaning or thinning in the sapling stage assumes
critical importance for guiding the composition and
growth of the future stand. Because this study was neither thinned nor cleaned, the known benefits of these
practices for furthering stand development and management objectives could not be quantified. On the other
hand, at age 15 longer term consequences of the overstocking on the different species could only be speculated upon by extrapolating trends in the first 15 years
of stand development. The additional 10 years of natural
stand development to age 25 provided a better basis for
testing of earlier conclusions on the apparent course of
mixed species stand development in overstocked natural
regeneration in the western larch type.
Results of this study to age 15 suggested that where
there had been little or no scarification or removal of
understory vegetation, intolerant species-especially
larch-were disadvantaged and expected to decline further in vigor and generally be poor prospects for future
management. At age 25, this expectation is less clear.
Western larch and lodgepole pine, both very shadeintolerant species, have maintained their relative positions of dominance and growth in the stand even where
no scarification or removal of competing understory
vegetation occurred. Apparently, once established with
other species in the western larch type, larch are able to
express dominance as well or better than other species.
This is not to suggest that choice and timing of seedbed
and competing vegetation treatments is not important.
Composition and relative growth of the different species
are strongly affected by seedbed and competing vegetation conditions and their resultant stand density effects.
From a management perspective, considerable flexibility is provided managers by seed-tree cutting in this forest type, when seedbed and vegetation conditions are
manipulated in the regeneration process. If the objective
is to maximize timber production on a short rotation,
scarification and removal of competing vegetation will
ensure prompt and predominant larch regeneration with
significant representation of spruce and Douglas-fir. But
growth rates will not meet short rotation objectives
unless stand density is controlled at an early age.
Because larch and lodgepole pine have regeneration and
growth advantages on disturbed sites, they have strong
timber production advantages; but the beginning of
growth decline due to overstocking during the 15- to
25-year age period demonstrates the need for early cleaning and spacing to enhance vigor and growth. On the
other hand, a delay in cleaning and thinning does not
appear as critical for the more shade-tolerant Douglasfir, subalpine fir, and spruce. Even though the treatment
areas that had not been scarified but had competing
vegetation removed had the best overall vigor and
growth after 25 years, it is possible that, had stand density been reduced, the early height growth advantage of
larch on scarified areas might have been maintained.
*U.S. GOVERNMENT PRINTING OFFICE:
1986-0-676-039/41,000
REFERENCES
Daubenmire, R.; Daubenmire, Jean B. Forest vegetation
of eastern Washington and northern Idaho. Technical
Bulletin 60. Pullman, W A: Washington Agricultural
Experiment Station; 1968. 104 p.
Pfister, R. D.; Kovalchik, D. B.; Arno, S. F.; Presby, R. C.
Forest habitat types of Montana. General Technical
Report INT-34. Ogden, UT: U.S. Department of
Agriculture, Forest Service, Intermountain Forest and
Range Experiment Station; 1977. 174 p.
Polk, R. Brooks; Boe, Kenneth N. Succession of trees in
cutover larch-Douglas-fir stands in western Montana.
Montana Academy of Science Proceedings. 10: 31-37;
1951.
Roe, Arthur L. Cutting practices in Montana larchDouglas-fir. Northwest Science. 29: 23-34; 1955.
Schmidt, Wyman C. Seedbed treatments influence seedling development in western larch forests. Research
Note INT-93. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range
Experiment Station; 1969. 7 p.
Schmidt, Wyman C.; Shearer, Raymond C.; Roe, Arthur L.
Ecology and silviculture of western larch forests. Technical Bulletin 1520. Washington, DC: U.S. Department
of Agriculture, Forest Service; 1976. 96 p.
Society of American Foresters. Forest cover types of the
United States and Canada. Eyre, F. H., ed. Washington,
DC; 1980. 148 p.
6
Cole, Dennis M.; Schmidt, Wyman C. Site treatments influence development of a
young mixed-species western larch stand. Research Paper INT-364. Ogden,
UT: U.S. Department of Agriculture, Forest Service, Intermountain Research
Station; 1986. 6 p.
Four treatments, all combinations of leaving or removing residual trees and
shrubs or scarifying or not scarifying seedbeds, were evaluated for species
differences in growth, vigor, and expression of dominance. Western larch was
the dominant species in regeneration and growth but had begun to lose some
of its advantage by age 25, particularly on scarified areas where overstocking
commonly occurred. Douglas-fir was less sensitive to the treatments and,
although significantly slower in absolute growth than larch, began to accelerate
after 15 years of age. This study confirms that early cleaning and thinning will
be necessary to achieve composition, density, and performance goals.
KEYWORDS: western larch, mixed species, stand development, regeneration
treatments, site preparation, vegetation control
INTERMOUNTAIN RESEARCH STATION
The Intermountain Research Station provides scientific knowledge and technology to improve management, protection, and use
of the forests and rangelands of the Intermountain West. Research
is designed to meet the needs of National Forest managers,
Federal and State agencies, industry, academic institutions, public
and private organizations, and individuals. Results of research are
made available through publications, symposia, workshops, training
sessions, and personal contacts.
The Intermountain Research Station territory includes Montana,
Idaho, Utah, Nevada, and western Wyoming. Eighty-five percent of
the lands in the Station area, about 231 million acres, are classified
as forest or rangeland. They include grasslands, deserts, shrublands, alpine areas, and forests. They provide fiber for forest industries, minerals and fossil fuels for energy and industrial development, water for domestic and industrial consumption, forage for
livestock and wildlife, and recreation opportunities for millions of
visitors.
Several Station units conduct research in additional western
States, or have missions that are national or international in scope.
Station laboratories are located in:
Boise, Idaho
Bozeman, Montana (in cooperation with Montana State
University)
Logan, Utah (in cooperation with Utah State University)
Missoula, Montana (in cooperation with the University of
Montana)
Moscow, Idaho (in cooperation with the University of Idaho)
Ogden, Utah
Provo, Utah (in cooperation with Brigham Young University)
Reno, Nevada (in cooperation with the University of Nevada)